Key Points:

New traffic-flow figures suggest our love of driving is waning, possibly because of rising fuel prices.

Figures for last month, given to the Weekend Herald by Transit NZ, show traffic on the city's motorways in peak hours is down an estimated 3 per cent since May last year.

That translates to a reduction of more than 6000 cars a day on some of the system's busiest stretches.

In the same period, Auckland's population rose by about 23,000, from 1,394,000 to about 1,417,000.

Transit's northern operations manager, Joseph Flannagan, said the average reduction in motorway traffic was about 3 per cent, but decreases of between 4 and 7 per cent were recorded at Great North Rd on the Northwestern Motorway, and at Silverdale, Oteha Valley Rd, Esmonde Rd and St Marys Bay on the Northern.

Falls of less than 1 per cent were recorded on the Southern Motorway and remaining Northwestern Motorway sites.

The only place where an increase was recorded was Mangere Bridge, on the Southwestern Motorway, where vehicle numbers were up 5 per cent.

Mr Flannagan said many factors could be contributing to the reduction in vehicle numbers, and it was impossible to say if it was the result of petrol price rises.

But other commentators say the cost of fuel is certainly a factor in the drop.

Automobile Association spokesman Simon Lambourne said it was apparent high petrol prices were forcing people to change their driving habits. Whether change was a long-term trend would not be known until fuel consumption figures were issued next month.

He warned against using the reduction as a reason to cut spending on Auckland's motorways.

"We still have significant congestion in the system, and parts of the picture to complete."

But Campaign for Better Transport convener Cameron Pitches said people were changing habits, avoiding unnecessary trips, car-pooling and taking their daily commute into account when moving house.

Heavy investment was needed in public transport to reflect those changes.

"Auckland is spending about $100 million a month on fuel. And that's
money draining straight out of our economy."

Huge investment and new services in Auckland's public transport system are also being touted as big reasons for Aucklanders' changing habits.

About 3.4 per cent more public transport passenger journeys were made in the year to May, compared to the year to May 2007. Rail trips in May this year were 21 per cent higher than the same month last year.

Green Party co-leader Jeanette Fitzsimons said the change in driving habits should herald a swing towards public transport funding in Auckland.

But future public transport investments were being pushed aside while motorway funding was secured.

Auckland's rail electrification was now in doubt as the expected regional fuel tax to provide the funding had lost favour in Parliament, she said.

Electrification of the rail system and converting Britomart to a through-station would enable passenger numbers to increase from 6 million a year now to 38 million, at a cost of about $2 billion.

A similar figure is being spent on the Western Ring Route's Waterview tunnel.

Ms Fitzsimons says this project should be scrapped and the money spent on rail, avoiding the need for any petrol tax.

Auckland Regional Transport Authority customer services general manager Mark Lambert said the shift from cars to public transport was partly driven by the cost of fuel.

But constant improvements to public transport services were giving people another option.